Axial Spondyloarthritis: Dual-Energy Virtual Noncalcium CT in the Detection of Bone Marrow Edema in the Sacroiliac Joints

Sacroiliac joint dysfunction: anatomy, pathophysiology, differential diagnosis, and treatment approaches

The sacroiliac joints (SIJ) play a pivotal role in pelvic stability and load transmission. SIJ-related disorders can pose a diagnostic challenge because of complex anatomy, non-specific imaging findings, and overlapping symptomatology with other lower back conditions. Broadly, SIJ pathology can be divided into the following categories: infectious, inflammatory, degenerative, mechanical, traumatic, and neoplastic. On the spectrum of mechanical disorders is the entity of SIJ dysfunction, defined as pain localized to the SIJ due to non-inflammatory causes. This paper aims to enhance the understanding of SIJ dysfunction by exploring SIJ anatomy, pathophysiology, and differential diagnosis for SIJ pain. Etiologies, associations, and diagnostic physical examination maneuvers for SIJ dysfunction are reviewed. We will discuss the role of diagnostic imaging in SIJ dysfunction and propose imaging findings which may indicate the diagnosis. Finally, we will discuss therapeutic strategies to treat SIJ dysfunction. By delving into the complexities of SIJ anatomy and pathophysiology, this paper provides valuable discernment for the diagnosis and management of SIJ-related disorders.

Dual-Energy Computed Tomography Applications in Rheumatology

Dual-energy computed tomography (DECT) has emerged as a transformative tool in the past decade. Initially employed in gout within the field of rheumatology to distinguish and quantify monosodium urate crystals through its dual-material discrimination capability, DECT has since broadened its clinical applications. It now encompasses various rheumatic diseases, employing advanced techniques such as bone marrow edema assessment, iodine mapping, and collagen-specific imaging. This review article aims to examine the unique characteristics of DECT, discuss its strengths and limitations, illustrate its applications for accurately evaluating various rheumatic diseases in clinical practice, and propose future directions for DECT in rheumatology.

Update of imaging in the assessment of axial spondyloarthritis

This update addresses new developments in imaging of axial spondyloarthritis from the past 5 years. These have focused mostly on enhanced CT and MRI-based technologies that bring greater precision to the assessment of both inflammatory and structural lesions in the sacroiliac joint. An international consensus has recommended a 4-sequence MRI for routine diagnostic evaluation of the sacroiliac joint aimed at depicting the location and extent of inflammation as well as an erosion-sensitive sequence for structural damage. The latter include high resolution thin slice sequences that accentuate the interface between subchondral bone and the overlying cartilage and joint space as well as synthetic CT, a deep learning-based technique that transforms certain MRI sequences into images resembling CT. Algorithms based on deep learning derived from plain radiographic, CT, and MRI datasets are increasingly more accurate at identifying sacroiliitis and individual lesions observed on images of the sacroiliac joints and spine.

Juvenile Idiopathic Arthritis and Spondylarthritis

Juvenile idiopathic arthritis (JIA) is a heterogeneous disorder affecting children < 16 years of age. The clinical heterogeneity translates to imaging, where no specific joint is affected. This article highlights a general imaging approach to JIA, using specific examples of the knee, hand, and wrist as the typical joints affected. We then focus on unique joints that are commonly affected by JIA: the temporomandibular joint, the joints of the upper cervical spine, and the sacroiliac joint. For these latter anatomical sites, regional anatomy and development, location-specific imaging considerations, and arthritis, treatment decision making, and potential differential considerations are reviewed. We highlight, where applicable, a multimodal approach to imaging using developed or developing standardized scoring systems.

Axial Spondyloarthritis: Updates in Concepts and Reporting in Radiology

Axial spondyloarthritis (axSpA) is a chronic inflammatory disease primarily affecting the axial skeleton, historically termed "human leukocyte antigen B27 positive spondyloarthropathy" or ankylosing spondylitis. Improved understanding of the underlying pathologic mechanisms has led to an ongoing redefinition of this disease state, a recognition of the substantial phenotypic and biological variation, and an emphasis on earlier detection. Magnetic resonance imaging has become central to identifying and confirming early axSpA, critical to fulfilling the promise of slowing disease progression and preventing irreversible structural abnormalities. We review the clinical background and current role of medical imaging in axSpA, with a focus on Assessment of SpondyloArthritis International Society consensus definitions, to improve radiology reporting and facilitate discussion between radiologists and other clinical experts in spondyloarthritis.

Dual-energy CT-derived virtual noncalcium imaging to assess bone marrow lesions in patients with knee osteoarthritis

To determine the diagnostic performance of dual-energy CT (DECT) virtual noncalcium (VNCa) technique in the detection of bone marrow lesions (BMLs) in knee osteoarthritis, and further analyze the correlation between the severity of BMLs on VNCa image and the degree of knee pain. 23 consecutive patients with clinically diagnosed knee osteoarthritis were underwent DECT and 3.0T MRI between August 2017 and November 2018. Evaluation of two pain assessment scales (WOMAC and KOOS) were collected. VNCa images and MRI were independently scored by three readers using a four-level scoring system over 15 anatomical subregions in each knee joint. Spearman correlation coefficient was used for total BML scores on DECT and MRI correlation with WOMAC and KOOS. Specificity, Sensitivity, NPV and PPV of reader 1 and reader 2 were 99.4%/99.2%, 89.4%/87.2%, 98.6%/98.3% and 95.5%/93.2%. A cutoff value of - 41.5 HU/- 46.5 HU provided sensitivities of 93.2%/90.9% and specificities of 100.0%/93.9% for diagnosing BMLs with AUC of 0.970/0.996. A stronger correlation was observed between the WOMAC and total BML score compared to the KOOS. DECT possessed excellent diagnostic performance in the detection of BMLs in knee osteoarthritis. And the pain degree increased with the severity of BMLs on VNCa images.

Diagnostic efficacy of dual-energy CT virtual non-calcium technique in the diagnosis of bone marrow edema of sacroiliac joints in ankylosing spondylitis

OBJECTIVE

In-depth investigation of the diagnostic performance of dual-energy CT (DECT) virtual non-calcium (VNCa) technique for sacroiliac joint bone marrow edema (BME) in patients with ankylosing spondylitis(AS).

METHODS

A total of 42 patients with AS)who underwent sacroiliac joint MRI and DECT scans on the same day at our Rheumatology and Immunology Department between August 2022 and June 2023 were selected. Using MRI as the reference standard, the presence of BME on the iliac and sacral surfaces was evaluated, resulting in the categorization of patients into BME-positive and BME-negative groups. Subsequently, the DECT scan data was processed using the "Bone Marrow" algorithm to generate VNCa color-coded images of the bone marrow. The diagnostic performance of DECT in detecting BME was assessed through visual qualitative evaluation and objective quantitative analysis.

RESULTS

Visual qualitative assessment analysis showed good agreement between the results of BME analysis on virtual non-calcium images and MRI images by both physicians (Kappa > 0.61). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of visual qualitative assessment for BME by Physicians A and B were as follows: iliac facet [(92.5%, 88.6%, 88.1%, 92.9%, 90.5%), (90.0%, 90.9%, 90.0%, 90.9%, 90.5%)], sacral facet [(88.4%, 87.8%, 88.4%, 87.8%, 88.1%), (90.7%, 85.3%, 86.7%, 89.7%, 88.1%)].In terms of objective quantitative analysis, the CT values of the edematous areas on the iliac and sacral surfaces were (-41.4 ± 15.9) Hu and (-38.8 ± 19.7) Hu, respectively, while the CT values of normal bone marrow areas were (-79.6 ± 18.2) Hu and (-72.8 ± 14.8) Hu, respectively. The CT values of the edematous areas were higher than those of the non-edematous areas. Based on the receiver operating characteristic curve analysis, the area under the curve for the iliac and sacral surfaces were 0.90 and 0.89, respectively. The optimal CT cutoff values were - 57.4 Hu and - 56.8 Hu, with corresponding sensitivities of 92.5% and 86.4% and specificities of 90.7% and 87.8%.

CONCLUSION

The DECT VNCa technique has a high diagnostic efficacy in the diagnosis of BME in the sacroiliac joints in ankylosing spondylitis in terms of visual qualitative assessment and objective quantitative analysis.

Axial Imaging in Spondyloarthritis

Imaging plays a crucial role in diagnosing and forecasting treatment outcomes in axial spondyloarthritis. Conventional radiography may overlook patients in the initial stages of the disease, while MRI is sensitive in identifying inflammation early on. Computed tomography reliably detects structural abnormalities. Practicing rheumatologists must possess a fundamental understanding of interpreting both active inflammatory and structural lesions in axial spondyloarthritis.

Diagnostic Value of Dual-Energy CT Virtual Noncalcium for the Assessment of Bone Marrow Edema of Wrist in Patients with Rheumatoid Arthritis

RATIONALE AND OBJECTIVES

To evaluate the value of dual-energy CT (DECT) virtual noncalcium (VNCa) images in the diagnosis of wrist bone marrow edema (BME) in patients with rheumatoid arthritis (RA).

MATERIALS AND METHODS

43 patients with wrist involvement in active RA prospectively underwent DECT and MRI. Functional DECT images reconstruction yielded VNCa images. MRI served as the reference standard for diagnosing BME. BME diagnosis differences between VNCa images and MRI were compared. Differences in CT values between BME and normal bone marrow were assessed. The optimal CT value for detecting BME in VNCa images was determined through ROC curve analysis. The correlation between VNCa images scores and RA disease activity was evaluated.

RESULTS

There was a high agreement between VNCa images and MRI in diagnosing BME (Kappa=0.831). VNCa images showed a significant difference in CT values between BME and normal bone marrow (P < 0.001). A cut-off value of - 54.8 HU yielded a sensitivity, specificity, and accuracy of 90.72%, 94.30%, and 93.33%, respectively, for detecting BME on VNCa images. The area under the ROC curve was 0.937 for distinguishing BME from normal bone marrow. Conventional CT images showed no statistically significant difference (P = 0.174) in CT values between BME and normal bone marrow. The VNCa images BME scores were positively correlated with RA disease activity (r = 0.399).

CONCLUSION

The DECT VNCa technique demonstrates its potential for diagnosing wrist BME in patients with RA and provides a valuable tool for assessing disease activity in RA.

IMPORTANT FINDINGS

The DECT VNCa technique has the ability to distinguish between BME and normal bone marrow. The VNCa images BME scores were positively correlated with the disease activity in RA.

Imaging of Sacroiliac Joints

The central role of imaging in diagnosing disorders affecting the sacroiliac joints (SIJs) necessitates a comprehensive understanding of the advantages, limitations, and potential pitfalls of the imaging techniques that can be used. In this article, the anatomy and biomechanics of SIJs are exposed, outlining their unique features, particularly the division into anteroinferior cartilaginous and postero-superior ligamentous parts. Overall, the goal of this article is to offer a comprehensive understanding of imaging techniques, anatomic complexity, and diagnostic considerations relevant to SIJs disorders, facilitating accurate diagnosis and patient management in clinical practice and research.

Dual-Energy Computed Tomography Applications in Rheumatology

Dual-energy computed tomography (DECT) has emerged as a transformative tool in the past decade. Initially employed in gout within the field of rheumatology to distinguish and quantify monosodium urate crystals through its dual-material discrimination capability, DECT has since broadened its clinical applications. It now encompasses various rheumatic diseases, employing advanced techniques such as bone marrow edema assessment, iodine mapping, and collagen-specific imaging. This review article aims to examine the unique characteristics of DECT, discuss its strengths and limitations, illustrate its applications for accurately evaluating various rheumatic diseases in clinical practice, and propose future directions for DECT in rheumatology.

Imaging of Sacroiliac Pain: The Current State-of-the-Art

Pain in the sacroiliac (SI) region is a common clinical manifestation, often caused by diseases involving the SI joints. This is typically due to inflammation or degenerative changes, while infections or cancer are less frequent causes. The SI joint is challenging to image accurately because of its distinct anatomical characteristics. For an accurate diagnosis, conventional radiography often needs to be supplemented with more precise methods such as magnetic resonance imaging (MRI) or computed tomography (CT). Sacroiliitis, a common presenting feature of axial spondyloarthritis (axial SpA), manifests as bone marrow edema, erosions, sclerosis, and joint space narrowing. Septic sacroiliitis and repetitive stress injuries in sports can also cause changes resembling inflammatory sacroiliitis. Other conditions, such as osteitis condensans ilii (OCI), can mimic the radiologic characteristics of sacroiliitis. Inflammatory lesions are diagnosed by concurrent erosions, hyperostosis, and ankylosis. Ligament ossifications or mechanical stress can also result in arthritic disorders. Determining the exact diagnosis can be aided by the distribution of the lesions. Inflammatory lesions can affect any part of the articulation, including the inferior and posterior portions. Mechanical lesions, such as those seen in OCI, often occur in the anterior middle region of the joint. In cases of idiopathic skeletal hyperostosis, ligament ossification is found at the joint borders. This pictorial essay describes common SI joint problems, illustrated with multimodal imaging data. We, also, discuss strategies for selecting the best imaging modalities, along with imaging pitfalls, key points, and approaches for treating patients with suspected inflammatory back pain.

Reporting Sacroiliac Joint Imaging Performed for Known or Suspected Axial Spondyloarthritis: Assessment of SpondyloArthritis International Society Recommendations

Whereas previous projects attempted to standardize imaging in patients with axial spondyloarthritis (axSpA), few studies have been published about the need for specific details regarding the image acquisition and lesions that may be less familiar to general radiologists. This work reports consensus recommendations developed by the Assessment of SpondyloArthritis International Society (ASAS) that aim to standardize the imaging reports in patients suspected of having or with known axSpA. A task force consisting of radiologists and rheumatologists from ASAS and one patient representative formulated two surveys that were completed by ASAS members. The results of these surveys led to the development of 10 recommendations that were endorsed by 73% (43 of 59) of ASAS members. The recommendations are targeted to the radiologist and include best practices for the inclusion of clinical information, technical details, image quality, and imaging findings in radiology reports. These recommendations also emphasize that imaging findings that indicate differential diagnoses and referral suggestions should be included in the concluding section of the radiology report. With these recommendations, ASAS aims to improve the diagnostic process and care for patients suspected of having or with known axSpA.

Dual-energy CT applications in musculoskeletal disorders

Dual-energy CT (DECT) is an exciting application in CT technology conferring many advantages over conventional single-energy CT at no additional with comparable radiation dose to the patient. Various emerging and increasingly established clinical DECT applications in musculoskeletal (MSK) imaging such as bone marrow oedema detection, metal artefact reduction, monosodium urate analysis, and collagen analysis for ligamentous, meniscal, and disc injuries are made possible through its advanced DECT post-processing capabilities. These provide superior information on tissue composition, artefact reduction and image optimization. Newer DECT applications to evaluate fat fraction for sarcopenia, Rho/Z application for soft tissue calcification differentiation, 3D rendering, and AI integration are being assessed for future use. In this article, we will discuss the established and developing applications of DECT in the setting of MSK radiology as well as the basic principles of DECT which facilitate them.

The Clinical Utility of Lower Extremity Dual-Energy CT Angiography in the Detection of Bone Marrow Edema in Diabetic Patients with Peripheral Artery Disease

(1) Background: Type 2 diabetes is a major cause of incidences and the progression of peripheral artery disease (PAD). Bone marrow edema (BME) is an important finding suggestive of underlying bone inflammation in non-traumatic diabetic patients with PAD. Our aim was to evaluate the presence, severity, and clinical implications of BME detected by virtual non-calcium application (VNCa) of dual-energy CT angiography (DE-CTA). (2) Methods: A consecutive series of 76 diabetic patients (55 men; mean age 71.6 ± 11.2 yrs) submitted to lower limb DE-CTA for PAD evaluation and revascularization planning, which were retrospectively analyzed. VNCa images were independently and blindly revised for the presence, location, and severity of BME by two radiologists with 10 years of experience. BME and non-BME groups were evaluated in terms of PAD clinical severity and 6-month secondary major amputation rate. (3) Results: BME was present in 17 (22%) cases, while 59 (78%) patients were non-BME. The BME group showed a significantly higher incidence of major amputation (p < 0.001) and a significantly higher number of patients with advanced clinical stages of PAD compared to the non-BME group (p = 0.024). (4) Conclusions: Lower limb DE-CTA with VNCa application is a useful tool in the detection of BME in diabetic patients with PAD, simultaneously enabling the evaluation of the severity and location of the arterial disease for revascularization planning. BME presence could be a marker of clinically severe PAD and a possible risk factor for revascularization failure.

Deep-learning for automated detection of MSU deposits on DECT: evaluating impact on efficiency and reader confidence

Introduction

Dual-energy CT (DECT) is a non-invasive way to determine the presence of monosodium urate (MSU) crystals in the workup of gout. Color-coding distinguishes MSU from calcium following material decomposition and post-processing. Manually identifying these foci (most commonly labeled green) is tedious, and an automated detection system could streamline the process. This study aims to evaluate the impact of a deep-learning (DL) algorithm developed for detecting green pixelations on DECT on reader time, accuracy, and confidence.

Methods

We collected a sample of positive and negative DECTs, reviewed twice-once with and once without the DL tool-with a 2-week washout period. An attending musculoskeletal radiologist and a fellow separately reviewed the cases, simulating clinical workflow. Metrics such as time taken, confidence in diagnosis, and the tool's helpfulness were recorded and statistically analyzed.

Results

We included thirty DECTs from different patients. The DL tool significantly reduced the reading time for the trainee radiologist (p = 0.02), but not for the attending radiologist (p = 0.15). Diagnostic confidence remained unchanged for both (p = 0.45). However, the DL model identified tiny MSU deposits that led to a change in diagnosis in two cases for the in-training radiologist and one case for the attending radiologist. In 3/3 of these cases, the diagnosis was correct when using DL.

Conclusions

The implementation of the developed DL model slightly reduced reading time for our less experienced reader and led to improved diagnostic accuracy. There was no statistically significant difference in diagnostic confidence when studies were interpreted without and with the DL model.

Clash of the titans: Current CT and CT-like imaging modalities in sacroiliitis in spondyloarthritis

Sacroiliitis is characterised by active and structural changes of the joint. While the Assessment of Spondyloarthritis international Society (ASAS) classification criteria stress the importance of bone marrow inflammation, recent reports suggest that osteitis can occur in various diseases, mechanical conditions and healthy individuals. Thus, structural lesions such as joint surface erosion and ankylosis are important factors for differential diagnosis. Various imaging modalities are available to examine these changes. However, computed tomography (CT) is generally considered the reference standard. Nonetheless, recent advances in magnetic resonance imaging (MRI) allow for direct bone imaging and the reconstruction of CT-like images that can provide similar information. This way, the ability of MRI to detect and measure structural lesions is strengthened. The aim of this review is to provide an overview of the pros and cons of CT and CT-like imaging modalities in sacroiliitis.

Diagnostic Value of Dual-Energy CT Virtual Non-Calcium and Rho/Z Images for Bone Marrow Infiltration in Primary Malignant Bone Tumors

RATIONALE AND OBJECTIVES

We investigated the diagnostic performance of dual-energy CT (DECT) virtual non-calcium (VNCa) and Rho/Z images for bone marrow infiltration of primary malignant bone tumors (PMBTs).

MATERIALS AND METHODS

We retrospectively analyzed 65 patients with PMBT who underwent DECT and MRI within 2 weeks. DECT was used to evaluate the presence and extent of marrow involvement surrounding PMBTs using the SCT, VNCa, and Rho/Z images. MRI was used as the reference standard for measurements. CT values of normal and involved bone marrow areas were measured on VNCa images, and Zeff values were measured on Rho/Z images. The statistical methods used were the 2*C chi-square test, ANOVA test, paired samples t test, and diagnostic performance of the different variables were evaluated using receiver operating characteristic curves.

RESULTS

VNCa and Rho/Z images showed higher accuracy (91%, 92% vs. 67%) and sensitivity (90%, 92% vs. 69%) than SCT images for diagnosing bone marrow infiltration in patients with PMBT. The maximum longitudinal diameter of tumor involvement measurements was statistically different between VNCa and SCT, Rho/Z and SCT, MRI, and SCT (all p < 0.05, p = 0.047, p = 0.049, and p = 0.023, respectively). The maximum transverse diameter was statistically significant between SCT and MRI, VNCa and MRI, Rho/Z and MRI (all p < 0.05, and p = 0.015, and p = 0.044, and p = 0.047, respectively). The HU or Zeff values based on the area of interest of VNCa and Rho/Z images differed significantly between the normal and infiltrated bone marrow area (p < 0.001). Receiver operating characteristic curve analysis revealed area under the curves of 0.995 and 0.988, respectively, with cut-off values of -31.57 HU and 7.8, and the sensitivity of both was 96.9%.

CONCLUSION

DECT-VNCa and Rho/Z images have good diagnostic value when evaluating bone marrow infiltration in PMBTs.

Preliminary evaluation of dual-energy CT to quantitatively assess bone marrow edema in patients with diabetic foot ulcers and suspected osteomyelitis

OBJECTIVES

The purpose of this study is to evaluate the value of dual-energy CT (DECT) with virtual non-calcium (VNCa) in quantitatively assessing the presence of bone marrow edema (BME) in patients with diabetic foot ulcers and suspected osteomyelitis.

METHODS

Patients with a diabetic foot ulcer and suspected osteomyelitis that underwent DECT (80 kVp/Sn150 kVp) with VNCa were retrospectively included. Two observers independently measured CT values of the bone adjacent to the ulcer and a reference bone not related to the ulcer. The patients were divided into two clinical groups, osteomyelitis or no-osteomyelitis, based on the final diagnosis by the treating physicians.

RESULTS

A total of 56 foot ulcers were identified of which 23 were included in the osteomyelitis group. The mean CT value at the ulcer location was significantly higher in the osteomyelitis group (- 17.23 ± 34.96 HU) compared to the no-osteomyelitis group (- 69.34 ± 49.40 HU; p < 0.001). Within the osteomyelitis group, the difference between affected bone and reference bone was statistically significant (p < 0.001), which was not the case in the group without osteomyelitis (p = 0.052). The observer agreement was good for affected bone measurements (ICC = 0.858) and moderate for reference bone measurements (ICC = 0.675). With a cut-off value of - 40.1 HU, sensitivity was 87.0%, specificity was 72.7%, PPV was 69.0%, and NPV was 88.9%.

CONCLUSION

DECT with VNCa has a potential value for quantitatively assessing the presence of BME in patients with diabetic foot ulcers and suspected osteomyelitis.

KEY POINTS

• Dual-energy CT (DECT) with virtual non-calcium (VNCa) is promising for detecting bone marrow edema in the case of diabetic foot ulcers with suspected osteomyelitis. • DECT with VNCa has the potential to become a more practical alternative to MRI in assessing the presence of bone marrow edema in suspected osteomyelitis when radiographs are not sufficient to form a diagnosis.

Musculoskeletal CT Imaging: State-of-the-Art Advancements and Future Directions

CT is one of the most widely used modalities for musculoskeletal imaging. Recent advancements in the field include the introduction of four-dimensional CT, which captures a CT image during motion; cone-beam CT, which uses flat-panel detectors to capture the lower extremities in weight-bearing mode; and dual-energy CT, which operates at two different x-ray potentials to improve the contrast resolution to facilitate the assessment of tissue material compositions such as tophaceous gout deposits and bone marrow edema. Most recently, photon-counting CT (PCCT) has been introduced. PCCT is a technique that uses photon-counting detectors to produce an image with higher spatial and contrast resolution than conventional multidetector CT systems. In addition, postprocessing techniques such as three-dimensional printing and cinematic rendering have used CT data to improve the generation of both physical and digital anatomic models. Last, advancements in the application of artificial intelligence to CT imaging have enabled the automatic evaluation of musculoskeletal pathologies. In this review, the authors discuss the current state of the above CT technologies, their respective advantages and disadvantages, and their projected future directions for various musculoskeletal applications.

Imaging in pediatric spondyloarthritis

PURPOSE OF REVIEW

Imaging is used in the diagnosis of peripheral and axial disease in juvenile spondyloarthritis (JSpA). Imaging of the joints and entheses in children and adolescents can be challenging for those unfamiliar with the appearance of the maturing skeleton. These differences are key for rheumatologists and radiologists to be aware of.

RECENT FINDINGS

In youth, skeletal variation during maturation makes the identification of arthritis, enthesitis, and sacroiliitis difficult. A great effort has been put forward to define imaging characteristics seen in healthy children in order to more accurately identify disease. Additionally, there are novel imaging modalities on the horizon that are promising to further differentiate normal physiologic changes versus disease.

SUMMARY

This review describes the current state of imaging, limitations, and future imaging modalities in youth, with key attention to differences in imaging interpretation of the peripheral joints, entheses, and sacroiliac joint in youth and adults.

Is it time to move on from pelvic radiography as the first-line imaging modality for suspected sacroiliitis?

PURPOSE OF REVIEW

Pelvic radiography in which structural lesions characteristic of sacroiliitis can be detected, is recommended as the first imaging modality when axial spondyloarthritis (axSpA) is suspected clinically. However, cross-sectional modalities like computed tomography (CT) and magnetic resonance imaging (MRI) are superior to radiographs for diagnosing sacroiliitis. Thus, we currently debate the role of radiography as first imaging modality in the diagnostic workup of axSpA.

RECENT FINDINGS

Diagnosing sacroiliitis on pelvic radiographs is challenging with large interobserver and intraobserver variation. Low-dose CT (ldCT) of the sacroiliac joints (SIJs) was proved to be more sensitive and reliable than radiographs with comparable ionizing radiation exposure. MRI is the preferred modality for detecting early SIJ inflammation, well before structural lesions evolve. New, promising MRI sequences sensitive to cortical bone improve erosion detection, making MRI a one-stop shop for the diagnosis of sacroiliitis.

SUMMARY

Given the debatable additive value of pelvic radiographs for the detection of sacroiliitis, and the presence of excellent alternatives for imaging the bony cortex of the SIJs such as ldCT and MRI with state-of-the-art sequences sensitive to cortical bone, it is high time to discuss the use of these more accurate modalities instead of radiographs.

Dual-energy CT virtual non-calcium: an accurate method for detection of knee osteoarthritis-related edema-like marrow signal intensity

OBJECTIVES

To evaluate the performance of a dual-energy computed tomography (DECT) virtual non-calcium (VNCa) technique in the detection of edema-like marrow signal intensity (ELMSI) in patients with knee joint osteoarthritis (OA) compared to magnetic resonance imaging (MRI).

METHODS

The study received local ethics board approval, and written informed consent was obtained. DECT and MRI were used to examine 28 knees in 24 patients with OA. VNCa images were generated by dual-energy subtraction of calcium. The knee joint was divided into 15 regions for ELMSI grading, performed independently by two musculoskeletal radiologists, with MRI as the reference standard. We also analyzed CT numbers through receiver operating characteristics and calculated cut-off values.

RESULTS

For the qualitative analysis, we obtained CT sensitivity (Readers 1, 2 = 83.7%, 89.8%), specificity (Readers 1, 2 = 99.5%, 99.5%), positive predictive value (Readers 1, 2 = 95.3%, 95.7%), and negative predictive value (Readers 1, 2 = 97.9%, 98.7%) for ELMSI. The interobserver agreement was excellent (κ = 0.92). The area under the curve for Reader 1 and Reader 2 was 0.961 (95% CI 0.93, 0.99) and 0.992 (95% CI 0.98, 1.00), respectively. CT numbers obtained from the VNCa images were significantly different between regions with and without ELMSI (p < .001).

CONCLUSIONS

VNCa images have good diagnostic performance for the qualitative and quantitative analysis of knee osteoarthritis-related ELMSI.

Axial Spondyloarthritis and Diagnostic Challenges: Over-diagnosis, Misdiagnosis, and Under-diagnosis

PURPOSE OF REVIEW

This article aims to review the challenges in axial spondyloarthritis diagnosis and identify the possible contributing factors.

RECENT FINDINGS

The inability to reach an accurate diagnosis in a timely fashion can lead to treatment delays and worse disease outcomes. The lack of validated diagnostic criteria and the misuse of the currently available classification criteria could be contributing. There is also significant inter-reader variability in interpreting images, and the radiologic definitions of axial spondyloarthritis continue to be re-defined to improve their positive predictive value. The role of inflammatory back pain features, serologic biomarkers, genetics, and their diagnostic contribution to axial spondyloarthritis continues to be investigated. There is still a significant amount of delay in the diagnosis of axial spondyloarthritis. Appreciating the factors that contribute to this delay is of utmost importance to close the gap. It is similarly important to recognize other conditions that may present with symptoms that mimic axial spondyloarthritis so that misdiagnosis and wrong treatment can be avoided.

Dual-Energy-CT for Osteitis and Fat Lesions in Axial Spondyloarthritis: How Feasible Is Low-Dose Scanning?

BACKGROUND

To assess the ability of low-dose dual-energy computed tomography (ld-DECT) virtual non-calcium (VNCa) images for detecting bone marrow pathologies of the sacroiliac joints (SIJs) in patients with axial spondyloarthritis (axSpA). Material and Methods: Sixty-eight patients with suspected or proven axSpA underwent ld-DECT and MRI of the SIJ. VNCa images were reconstructed from DECT data and scored for the presence of osteitis and fatty bone marrow deposition by two readers with different experience (beginner and expert). Diagnostic accuracy and correlation (Kohen's k) with magnetic resonance imaging (MRI) as the reference standard were calculated for the overall and for each reader separately. Furthermore, quantitative analysis was performed using region-of-interest (ROI) analysis. Results: Twenty-eight patients were classified as positive for osteitis, 31 for fatty bone marrow deposition. DECT's sensitivity (SE) and specificity (SP) were 73.3% and 44.4% for osteitis and 75% and 67.3% for fatty bone lesions, respectively. The expert reader achieved higher diagnostic accuracy for both osteitis (SE 93.33%; SP: 51.85%) and fatty bone marrow deposition (SE: 65%; SP: 77.55%) than the beginner (SE: 26.67%; SP: 70.37% for osteitis; SE: 60%; SP: 44.9% for fatty bone marrow deposition). Overall correlation with MRI was moderate (r = 0.25, p = 0.04) for osteitis and fatty bone marrow deposition (r = 0.25, p = 0.04). Fatty bone marrow attenuation in VNCa images (mean: -129.58 HU; ±103.61 HU) differed from normal bone marrow (mean: 118.84 HU, ±99.91 HU; p < 0.01) and from osteitis (mean: 172 HU, ±81.02 HU; p < 0.01) while osteitis did not differ significantly from normal bone marrow (p = 0.27). Conclusion: In our study, low-dose DECT failed to detect osteitis or fatty lesions in patients with suspected axSpA. Thus, we conclude that higher radiation might be needed for DECT-based bone marrow analysis.

Hounsfield Units measured in low dose CT reliably assess vertebral trabecular bone density changes over two years in axial spondyloarthritis

OBJECTIVES

To describe low dose Computed Tomography (ldCT) Hounsfield Units (HU) two-year change-from-baseline values (expressing trabecular bone density changes) and analyse their inter-reader reliability per vertebra in radiographic axial spondyloarthritis (r-axSpA).

METHODS

We used 49 patients with r-axSpA from the multicentre two-year Sensitive Imaging in Ankylosing Spondylitis (SIAS) study. LdCT HU were independently measured by two trained readers at baseline and two years. Mean (standard deviation, SD) for the change-from-baseline HU values were provided per vertebra by reader. Intraclass correlation coefficients (ICC; absolute agreement, two-way random effect), Bland-Altman plots and smallest detectable change (SDC) were obtained. Percentages of vertebrae in which readers agreed on the direction of change and on change >|SDC| were computed.

RESULTS

Overall, 1,053 (98% of all possible) vertebrae were assessed by each reader both at baseline and two years. Over two years, HU mean change values varied from -23 to 28 and 29 for reader 1 and 2, respectively. Inter-reader reliability of the two-year change-from-baseline values per vertebra was excellent: ICC:0.91-0.99; SDC:6-10; Bland-Altman plots were homoscedastic, with negligible systematic error between readers. Readers agreed on the direction of change in 88-96% and on change >|SDC| in 58-94% of vertebrae, per vertebral level, from C3 to L5. Overall, similar results were obtained across all vertebrae.

CONCLUSION

LdCT measurement of HU is a reliable method to assess two-year changes in trabecular bone density at each vertebra from C3-L5. Being reliable across all vertebrae, this methodology can aid the study of trabecular bone density changes over time in r-axSpA, a disease affecting the whole spine.

Advances in Bone Marrow Imaging: Strengths and Limitations from a Clinical Perspective

Conventional magnetic resonance imaging (MRI) remains the modality of choice to image bone marrow. However, the last few decades have witnessed the emergence and development of novel MRI techniques, such as chemical shift imaging, diffusion-weighted imaging, dynamic contrast-enhanced MRI, and whole-body MRI, as well as spectral computed tomography and nuclear medicine techniques. We summarize the technical bases behind these methods, in relation to the common physiologic and pathologic processes involving the bone marrow. We present the strengths and limitations of these imaging methods and consider their added value compared with conventional imaging in assessing non-neoplastic disorders like septic, rheumatologic, traumatic, and metabolic conditions. The potential usefulness of these methods to differentiate between benign and malignant bone marrow lesions is discussed. Finally, we consider the limitations hampering a more widespread use of these techniques in clinical practice.

Use of Imaging in Axial Spondyloarthritis for Diagnosis and Assessment of Disease Remission in the Year 2022

Medical imaging remains the cornerstone of diagnostics and follow-up of axial spondyloarthritis (axSpA) patients. With the lack of specific biomarkers allowing monitoring of disease activity and progression, clinicians refer to imaging modalities for accurate evaluation of the axSpA burden. Technological advances and increasing availability of modern imaging techniques such as MRI have enabled faster diagnosis of the disease, hence dramatically changed the diagnostic delay and improved the prognosis and functional outcomes for axSpA patients.Active sacroiliitis as visualized by MRI has been widely accepted as a diagnostic tool, and definitions of inflammatory and structural lesions within the axial skeleton have been developed. Recently, it has been acknowledged that bone marrow edema, suggestive of sacroiliitis, is a common finding among non-SpA patients, and could be attributed to mechanical loading or accumulate with age in healthy individuals. Therefore, it is crucial to distinguish between true pathological and concealing imaging findings, not only for diagnostic but also for disease remission purposes. New imaging modalities, aimed for in vivo visualization of specific molecular processes, could be employed to cross-validate findings from techniques used in daily clinical practice. This review critically evaluates the use of different imaging modalities for diagnosis and assessment of disease remission in axSpA in the year 2022.

Synthetic MRI in the detection and quantitative evaluation of sacroiliac joint lesions in axial spondyloarthritis

Objective

Our primary objective was to verify the hypothesis that synthetic magnetic resonance imaging (MRI) is similar to conventional MRI in detecting sacroiliac joint lesions in patients with axial spondyloarthritis (axSpA). A secondary objective was to assess the quantitative value of synthetic mapping in bone marrow edema (BME) and fat metaplasia.

Methods

A total of 132 axSpA patients who underwent synthetic and conventional MRI from October 2019 to March 2021 were included in this prospective study. Two independent readers visually evaluated active inflammatory (BME, capsulitis, enthesitis, and inflammation at site of erosion) and structural lesions (erosion, sclerosis, ankylosis, and fat metaplasia) of the sacroiliac joints on conventional and synthetic magnetic resonance (MR) images. In addition, T1, T2, and proton density (PD) values, which were generated by synthetic mapping, were used to further quantitatively evaluate BME and fat metaplasia. A McNemar test was used to compare the differences between the two methods in the detection of sacroiliac joint lesions. Intraclass correlation coefficients (ICCs) were used to assess the inter-reader consistency of quantitative values. Mann-Whitney tests were performed, and receiver operating characteristic (ROC) curves were created for all quantitative analyses.

Results

There were no statistical difference between synthetic and conventional MRI in the detection of sacroiliac joint lesions (all p-values > 0.05). A total of 103 images of BME and 111 images of fat metaplasia were quantitatively evaluated using T1, T2, and PD values. The consistency of quantitative values among readers was good (ICC 0.903-0.970). T1 and T2 values were consistently higher in BME than in normal marrow (p < 0.001), but PD values were not significantly different (p = 0.830). T2 and PD values were higher in fat metaplasia than in normal marrow, but T1 values were lower (p < 0.001). In the case of BME, T1 values had greater diagnostic efficiency [area under the curve (AUC) 0.99] than T2 values (AUC 0.78). There were no significant differences in the diagnostic efficiency of T1 (AUC 0.88), T2 (AUC 0.88), and PD (AUC 0.88) values in the case of fat metaplasia.

Conclusion

Synthetic MRI is as effective as conventional MRI in detecting sacroiliac joint lesions in patients with axSpA. Furthermore, synthetic mapping can accurately quantify BME and fat metaplasia.

Novel imaging techniques for sacroiliac joint assessment

PURPOSE OF REVIEW

Imaging of the sacroiliac joints is one of the cornerstones in the diagnosis and monitoring of axial spondyloarthritis. We aim to present an overview of the emerging imaging techniques for sacroiliac joint assessment and provide an insight into their relevant benefits and pitfalls.

RECENT FINDINGS

Evaluation of structural and active inflammatory lesions in sacroiliitis are both important for understanding the disease process. Dual-energy computed tomography (CT) can detect inflammatory bone marrow edema in the sacroiliac joints and provides an alternative for magnetic resonance imaging (MRI). Three-dimensional gradient echo sequences improve the visualization of erosions on MRI. Susceptibility weighted MRI and deep learning-based synthetic CT are innovative MRI techniques that allow for generating 'CT-like' images and better depict osseous structural lesions than routine MRI sequences.

SUMMARY

New imaging innovations and developments result in significant improvements in the imaging of spondyloarthritis. Advanced MRI techniques enhance its potential for the accurate detection of structural and active inflammatory lesions of sacroiliitis in one single imaging session.

Future of Low-Dose Computed Tomography and Dual-Energy Computed Tomography in Axial Spondyloarthritis

Purpose of Review

Recent technical advances in computed tomography (CT) such as low-dose CT and dual-energy techniques open new applications for this imaging modality in clinical practice and for research purposes. This article will discuss the latest innovations and give a perspective on future developments.

Recent Findings

Low-dose CT has increasingly been used for assessing structural changes at the sacroiliac joints and the spine. It has developed into a method with similar or even lower radiation exposure than radiography while outperforming radiography for lesion detection. Despite being incompatible with low-dose scanning, some studies have shown that dual-energy CT can provide additional information that is otherwise only assessable with magnetic resonance imaging (MRI). However, it is unclear whether this additional information is reliable enough and if it would justify the additional radiation exposure, i.e. whether the performance of dual-energy CT is close enough to MRI to replace it in clinical practice.

Summary

While the role of dual-energy CT in patients with axial spondyloarthritis remains to be established, low-dose CT has developed to an appropriate modality that should replace radiography in many circumstances and might supplement MRI.

Choose wisely: imaging for diagnosis of axial spondyloarthritis

OBJECTIVE

To assess the diagnostic accuracy of radiography (X-ray, XR), CT and MRI of the sacroiliac joints for diagnosis of axial spondyloarthritis (axSpA).

METHODS

163 patients (89 with axSpA; 74 with degenerative conditions) underwent XR, CT and MR. Three blinded experts categorised the imaging findings into axSpA, other diseases or normal in five separate reading rounds (XR, CT, MR, XR +MR, CT +MR). The clinical diagnosis served as reference standard. Sensitivity and specificity for axSpA and inter-rater reliability were compared.

RESULTS

XR showed lower sensitivity (66.3%) than MR (82.0%) and CT (76.4%) and also an inferior specificity of 67.6% vs 86.5% (MR) and 97.3% (CT). XR +MR was similar to MR alone (sensitivity 77.5 %/specificity 87.8%) while CT+MR was superior (75.3 %/97.3%). CT had the best inter-rater reliability (kappa=0.875), followed by MR (0.665) and XR (0.517). XR +MR was similar (0.662) and CT+MR (0.732) superior to MR alone.

CONCLUSIONS

XR had inferior diagnostic accuracy and inter-rater reliability compared with cross-sectional imaging. MR alone was similar in diagnostic performance to XR+MR. CT had the best accuracy, strengthening the importance of structural lesions for the differential diagnosis in axSpA.

Addition of CT to Improve the Diagnostic Confidence for the Detection of Sacroiliac Joint Erosions in Patients with Equivocal MRI Findings

PURPOSE

To determine if CT can improve the diagnostic confidence for the detection of sacroiliac joint (SIJ) erosions in patients with equivocal MRI findings.

METHODS

A retrospective analysis of adult patients who had an SIJ MRI and a subsequent SIJ CT within 12 months was conducted. Using a 5-point Likert scale, two reviewers evaluated the de-identified MRI and CT images in randomized order and in separate sessions to answer the question: "Does the patient have SIJ erosions?". A Fisher's exact test was used to analyze the difference in diagnostic confidence, and intraclass correlation coefficient (ICC) was used to determine interrater reliability.

RESULTS

54 patients were included in the analysis (average age, 43.9 years). The average time interval between initial SIJ MRI and subsequent CT was 14.4 weeks (range, 5.6-50.3 weeks). CT resulted in significantly more cases with definitive diagnostic confidence than cases with probable or equivocal confidence compared to MRI (P < .001). Amongst cases with equivocal findings on MRI, 73.2% of cases had definitive diagnoses on CT. There was moderate interrater agreement for MRI, with an ICC of .490 [95% CI, .258-.669], and excellent agreement for CT, with an ICC of .832 [95% CI, .728-.899].

CONCLUSION

Overall, CT led to significantly increased diagnostic confidence and higher interrater reliability for the detection of SIJ erosions compared to MRI. Judicious use of CT may be useful in detecting SIJ erosions in patients with equivocal MRI findings.

ACR Appropriateness Criteria® Inflammatory Back Pain: Known or Suspected Axial Spondyloarthritis: 2021 Update

Inflammatory back pain is a hallmark feature of axial spondyloarthritis, a heterogeneous group of inflammatory disorders which affects the sacroiliac joints and spine. Imaging plays a key role in diagnosis of this disease and in facilitating appropriate treatment. This document provides evidence-based recommendations on the appropriate use of imaging studies during multiple stages of the clinical evaluation of patients with suspected or known axial spondyloarthritis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Beyond the sacro-Iliac joints: Vertebral involvement in axial spondylarthritis

Imaging plays a central role in the diagnosis of axial spondylarthritis (axSpA). Commonly the sacroiliac joints are involved but vertebral involvement can occur in isolation in 1 out of 4 patients. Recognizing vertebral involvement patterns in axSpA can help establishing a diagnosis early and initiate therapy before irreversible changes have occurred. Magnetic resonance imaging (MRI) is considered the reference standard for early detection of inflammatory changes of the disease. Aims of this review are to present an overview of the imaging findings of vertebral involvement in axSpA, and to detail the current recommendations on the role of imaging in the diagnosis of axSpA in patients with isolated vertebral involvement.

Anatomical analysis of inflammation in hand psoriatic arthritis by Dual-Energy CT Iodine Map

OBJECTIVE

This study aimed to identify the detailed location of inflammatory lesions and its frequency of hand PsA on DECT Iodine Map with referring the cadaveric specimen.

MATERIALS AND METHODS

Thirty-eight anatomical landmarks were selected as a potential inflammatory sites in the thumb and middle finger. We included 22 symptomatic PsA patients who underwent contrast enhanced DECT of the hand. MR images and macroscopic specimens of thumb and middle finger were prepared from a cadaver. Two musculoskeletal radiologists evaluated DECT with referring the cadaveric images to determine the precise location of inflammatory sites and its frequency.

RESULTS

The frequently observed inflammation sites of active PsA patients were either classical or functional entheses, and coincide with the well-known hypothesis that primary inflammatory sites of PsA are enthesis. We have noticed that there was remarkable enhancement around DIP joints (13.6 %-45.5 %).

CONCLUSION

DECT could assess the detailed anatomical sites of the inflammatory lesion in hand psoriatic arthritis, which coincided with enthesis.

Virtual non-calcium dual-energy CT: clinical applications

Dual-energy CT (DECT) has emerged into clinical routine as an imaging technique with unique postprocessing utilities that improve the evaluation of different body areas. The virtual non-calcium (VNCa) reconstruction algorithm has shown beneficial effects on the depiction of bone marrow pathologies such as bone marrow edema. Its main advantage is the ability to substantially increase the image contrast of structures that are usually covered with calcium mineral, such as calcified vessels or bone marrow, and to depict a large number of traumatic, inflammatory, infiltrative, and degenerative disorders affecting either the spine or the appendicular skeleton. Therefore, VNCa imaging represents another step forward for DECT to image conditions and disorders that usually require the use of more expensive and time-consuming techniques such as magnetic resonance imaging, positron emission tomography/CT, or bone scintigraphy. The aim of this review article is to explain the technical background of VNCa imaging, showcase its applicability in the different body regions, and provide an updated outlook on the clinical impact of this technique, which goes beyond the sole improvement in image quality.

Imaging update in inflammatory arthritis

Ultrasonography and magnetic resonance imaging have become important imaging modalities in rheumatological disorders next to standard radiography. Due to their ability to assess both morphological and functional changes they play a significant role in early diagnosis and treatment monitoring. This review presents the latest advancements in imaging of inflammatory arthritis with a focus on two main groups of rheumatic diseases: connective tissue diseases and spondyloarthritis. New developments related to peripheral and sacroiliac joints imaging are discussed, including Superb Micro Flow Imaging and Shear Wave Elastography in ultrasonography, as well as Whole Body MRI, quantitative MRI, and the recent advances in cartilage imaging in MRI, including T2-and T1p-mapping, and dGEMRIC. The role of emerging imaging techniques in the early diagnosis of inflammatory arthritis is discussed, including DECT, VIBE, BoneMRI, and pQCT.

Identification of Non-Traumatic Bone Marrow Oedema: The Pearls and Pitfalls of Dual-Energy CT (DECT)

Dual-energy computed tomography (DECT) is an imaging technique widely used in traumatic settings to diagnose bone marrow oedema (BME). This paper describes the role of DECT in diagnosing BME in non-traumatic settings by evaluating its reliability in analyzing some of the most common painful syndromes. In particular, with an illustrative approach, the paper describes the possible use of DECT for the evaluation of osteochondral lesions of the knee and of the ankle, avascular necrosis of the hip, non-traumatic stress fractures, and other inflammatory and infectious disorders of the bones.

Imaging update in spondyloarthropathy

Although our understanding of axial spondyloarthropathy (axSpA) has increased recently, there has not been a concurrent improvement in patient diagnosis with delays contributing to patient morbidity. Imaging findings of axSpA can be subtle and may be dismissed often due to lack of understanding by reporters and importantly clinicians who do not suspect the disease. Recognition of the importance of imaging has led to the inclusion of MRI as part of the diagnostic criteria for axSpA. With this in mind, a number of advancements have been made in an attempt to increase our diagnostic accuracy on imaging. This article will give an overview of these techniques as well as a recap of the imaging features of axSpA.

Low-dose computed tomography for axial spondyloarthritis: update on use and limitations

PURPOSE OF REVIEW

Recent developments in low-dose computed tomography (ldCT) have greatly reduced radiation exposure levels. This article reviews what a ldCT is and its use and limitations for imaging axial spondyloarthritis.

RECENT FINDINGS

Detection of structural damage in bone with CT is far superior to radiography and ldCT of the sacroiliac joints (SIJ) can now be done at radiation exposure levels equivalent to, or even less than, conventional radiography. ldCT should be considered a 'first-choice' test for arthritis imaging, and wherever available, SIJ ldCT may completely replace conventional radiography. Radiation exposure in the spine with ldCT is lower than conventional CT. However, it is unclear whether the additional information regarding structural damage changes in the spine provided by ldCT will alter patient management sufficiently often to merit switching from spinal radiography to ldCT in routine clinical practice. In addition, ldCT cannot assess osteitis disease activity for which MRI remains the best test.

SUMMARY

ldCT of the sacroiliac joints (SIJ) can be done at radiation exposure levels equivalent to, or less than, radiography and ldCT may completely replace SIJ radiography. However, the role of spinal ldCT for spondyloarthritis is not clear and MRI is far superior for detecting disease activity.

Dual-Energy Computed Tomography Virtual Noncalcium Technique in Diagnosing Osteoporosis: Correlation With Quantitative Computed Tomography

OBJECTIVE

The aim of this study was to evaluate dual-energy computed tomography (CT) virtual noncalcium (VNCa) technique as a means of quantifying osteoporosis.

METHODS

Dual-energy CT scans were obtained prospectively, targeting lumbar regions of 55 patients with chronic low back pain. A standard quantitative CT (QCT) phantom was positioned at the waist during each procedure, using proprietary software (QCT Pro; Mindways, Tex) to measure bone mineral density (BMD) in each vertebral body. Vendor dual-energy analytic software was altered with a specially modified configuration file to produce a "Virtual Non Calcium" or "VNCa" output, as such output variables were remapped to produce the following calcium values rather than iodine, yielding the following QCT parameters: CT value of calcium (originally "contrast media" [CM]), CT value of mixed energy imaging (regular CT value [rCT]), calcium density (originally "contrast agent density" [CaD]), and fat fraction (FF). Pearson test served to assess correlations between BMD and these parameters. Multiple linear regression analysis was applied to construct an equation for generating regressive BMD (rBMD) values. In gauging diagnostic accuracies, the criterion-standard BMD cutoff point (<80 mg/cm3) was adopted for QCT, whereas the rBMD threshold was defined by receiver operating characteristic curve.

RESULTS

Contrast media, rCT, CaD, and FF values (reflecting CT value of calcium, regular CT value, calcium density, and fat fraction, respectively) significantly correlated with BMD (r values: 0.885, 0.947, 0.877, and 0.492, respectively; all P < 0.01). Contrast media, CaD, and FF showed independent associations with BMD; the regressive equation was formulated as follows: rBMD = 54.82 - 0.19 × CM + 20.03 × CaD - 1.24 × FF. The area under the curve of rBMD in diagnosing osteoporosis was 0.966 ± 0.009 (P < 0.01). At an rBMD threshold of less than 81.94 mg/cm3, sensitivity and specificity were 90.0% and 92.0%, respectively.

CONCLUSIONS

Dual-energy CT VNCa technique may constitute a valid alternative method for quantifying the mineral content and marrow fat composition of bone in diagnostic assessments of osteoporosis.

Diagnostic performance of plain radiography for sacroiliitis in patients with suspected axial spondyloarthritis: a systematic review and meta-analysis

BACKGROUND

Plain radiography serves a pivotal role in diagnosing axial spondyloarthritis. However, a broad range of diagnostic performance of plain radiography has been reported.

PURPOSE

To perform a systematic review and meta-analysis to measure the diagnostic performance of plain radiography for sacroiliitis in patients suspected of having axial spondyloarthritis using magnetic resonance imaging (MRI) findings as the reference standard.

MATERIAL AND METHODS

Studies comparing radiography and MRI in the diagnosis of sacroiliitis in patients suspected of having axial spondyloarthritis were searched in PubMed and EMBASE. Additionally, studies analyzed SPondyloaArthritis Caught Early (SPACE), DEvenir des Spondylarthropathies Indifferenciées Récentes (DESIR), GErman Spondyloarthritis Inception Cohort (GESPIC), and South Swedish Arthritis Treatment Group (SSATG) cohorts were manually searched. Pooled sensitivity and specificity of radiography were calculated by using a bivariate random-effects model. Meta-regression analyses were performed to identify the sources of heterogeneity.

RESULTS

Eight eligible studies with 1579 patients were included. The pooled sensitivity and specificity of radiography were 0.55 (95% confidence interval [CI] = 0.40-0.69) and 0.87 (95% CI = 0.72-0.95). The meta-regression analyses showed prospective study design and criteria for MRI positivity considering only active bone marrow edema were associated with lower sensitivity.

CONCLUSION

The plain radiography showed low sensitivity and reasonable specificity in diagnosis of sacroiliitis in patients suspected of having axial spondyloarthritis.

Detection of bone marrow edema in osteonecrosis of the femoral head using virtual noncalcium dual-energy computed tomography

PURPOSE

To determine the diagnostic performance of virtual noncalcium (VNCa) dual-energy computed tomography (DECT) in the detection of bone marrow edema (BME) in participants with osteonecrosis of the femoral head (ONFH).

METHODS

In this prospective study, 24 consecutive participants (15 men, 9 women; mean age, 44 years, range, 21-72 years) diagnosed with ONFH who underwent DECT and magnetic resonance imaging (MRI) between September 2019 and January 2020 were involved. Two independent readers visually evaluated color-coded VNCa images using a binary classification (0 = normal bone marrow, 1 = BME). MRI served as the reference standard for the presence of BME. Interobserver agreement for the visual evaluation of VNCa DECT images was calculated with κ statistics. We determined computed tomography (CT) numbers on VNCa images and weighted-average CT sets using region-of-interest-based quantitative analysis. The t-test was used to compare the differences of CT values between BME areas and normal bone marrow areas. Receiver operating characteristic (ROC) curve was used to select an optimal CT values of VNCa images for detecting BME. A p value of <0.05 was considered as statistically significant.

RESULTS

The sensitivity, specificity, and accuracy of Reader 1 and Reader 2, respectively, in the identification of BME at DECT were 95 % and 89 % (18 and 17 of 19), 96 % and 96 % (25 and 25 of 26), and 93 % (43 and 42 of 45). Interobserver agreement was excellent (κ = 0.86). The VNCa CT numbers of the BME area and the normal bone marrow area were -28.6 (-17.9--39.4) HU and -97.9 (-91.3--104.4) HU, respectively, with statistical significance (t = -10.6, p < 0.001). The weighted-average CT numbers of the BME area and the normal bone marrow area were 152.4(122.2-182.7) HU and 121.1(103.6-183.6) HU, respectively, with no statistical significance (t = -2.0, p > 0.05). The area under the receiver operating characteristic curve was 0.99 in differentiation of the BME from normal bone marrow. A cut-off value of -57.2 HU yielded overall sensitivity, specificity, and accuracy, respectively, of 95 % (18 of 19), 100 % (26 of 26), and 98 % (44 of 45) detection of BME in participants with ONFH.

CONCLUSION

Visual and quantitative analyses of VNCa images shows excellent diagnostic performance for assessing BME in participants with ONFH.

Recognizing and Minimizing Artifacts at Dual-Energy CT

Dual-energy CT (DECT) is an exciting innovation in CT technology with profound capabilities to improve diagnosis and add value to patient care. Significant advances in this technology over the past decade have improved our ability to successfully adopt DECT into the clinical routine. To enable effective use of DECT, one must be aware of the pitfalls and artifacts related to this technology. Understanding the underlying technical basis of artifacts and the strategies to mitigate them requires optimization of scan protocols and parameters. The ability of radiologists and technologists to anticipate their occurrence and provide recommendations for proper selection of patients, intravenous and oral contrast media, and scan acquisition parameters is key to obtaining good-quality DECT images. In addition, choosing appropriate reconstruction algorithms such as image kernel, postprocessing parameters, and appropriate display settings is critical for preventing quantitative and qualitative interpretive errors. Therefore, knowledge of the appearances of these artifacts is essential to prevent errors and allows maximization of the potential of DECT. In this review article, the authors aim to provide a comprehensive and practical overview of possible artifacts that may be encountered at DECT across all currently available commercial clinical platforms. They also provide a pictorial overview of the diagnostic pitfalls and outline strategies for mitigating or preventing the occurrence of artifacts, when possible. The broadening scope of DECT applications necessitates up-to-date familiarity with these technologies to realize their full diagnostic potential.

Dual energy computed tomography evaluation of skeletal traumas

Skeletal traumas are among the most common routine challenges faced by Emergency Radiologists, in particular in case of radiographically occult nondisplaced fractures or in case of soft tissue injuries. With the development of Dual Energy Computed Tomography (DECT) technology, new post-processing applications have gained a useful diagnostic role in many fields of musculoskeletal imaging including acute skeletal trauma imaging. In addition to conventional CT images, DECT allows for the generation of virtual calcium-suppressed images subtracting calcium from unenhanced CT images based on the fact that material attenuation varies at different energy levels. In this way, virtual-non-calcium (VNC) images can precisely characterize traumatic bone marrow edema in both axial and appendicular skeleton, facilitating prompt clinical decision, especially when magnetic resonance method is contraindicated or unavailable. Other DECT emerging applications in the trauma setting include metal artifact reduction and collagen mapping for the evaluation of injuries affecting ligament, tendon, and intervertebral disk. This review focuses on the basic principles of DECT and related post-processing algorithms, highlighting the current advantages and limitations of these new imaging advances in the Emergency Department related to skeletal traumas.

Update of imaging in the diagnosis and management of axial spondyloarthritis

Imaging of the spine and sacroiliac joints has acquired a central role in the diagnosis and classification of axial spondyloarthritis (axSpA) in the earliest phases of the disease. New definitions of specific imaging lesions, particularly in magnetic resonance imaging (MRI), have been recently updated and revised by the ASAS MRI working group to reach a standardized understanding and diagnosis of axSpA among rheumatologists. Recognizing the misleading pitfalls of MRI lesions and differential diagnosis also represents an essential issue in clinical practice to avoid false-positive findings and establish the diagnosis of axSpA with careful regard to the clinical context, clinical signs, and biological tests. This review summarizes the current evidence on the different imaging modalities of the sacroiliac joints and the spine with their application in the clinical setting of SpA and their main pitfalls; it also highlights the newest emerging imaging techniques.

Quantitative Imaging in Inflammatory Arthritis: Between Tradition and Innovation

Radiologic imaging is crucial for diagnosing and monitoring rheumatic inflammatory diseases. Particularly the emerging approach of precision medicine has increased the interest in quantitative imaging. Extensive research has shown that ultrasound allows a quantification of direct signs such as bone erosions and synovial thickness. Dual-energy X-ray absorptiometry and high-resolution peripheral quantitative computed tomography (CT) contribute to the quantitative assessment of secondary signs such as osteoporosis or lean mass loss. Magnetic resonance imaging (MRI), using different techniques and sequences, permits in-depth evaluations. For instance, the perfusion of the inflamed synovium can be quantified by dynamic contrast-enhanced imaging or diffusion-weighted imaging, and cartilage injury can be assessed by mapping (T1ρ, T2). Furthermore, the increased metabolic activity characterizing the inflammatory response can be reliably assessed by hybrid imaging (positron emission tomography [PET]/CT, PET/MRI). Finally, advances in intelligent systems are pushing forward quantitative imaging. Complex mathematical algorithms of lesions' segmentation and advanced pattern recognition are showing promising results.